Prepare the fish and seafood. Gut the larger fish and cut into pieces. The small rock fish can be used whole, but it is a good idea to gut them.
Heat half the oil in a saucepan and sauté the previously peeled and finely sliced leek, onion and garlic until golden. Add the peeled and chopped tomatoes, herbs and spices and leave to simmer over a low heat for 10 minutes, stirring occasionally.
Add the prawns or shrimps and crayfish, sauté quickly.
Incorporate the rest of the fish along with the cleaned mussels and clams, (leave the largest pieces of fish until the end).
Season to taste, add the rest of the oil and the saffron and cover with hot water.
Cook for 10-15 minutes, add the remaining fish and leave to cook for 10 minutes.
Serve with toasted crusty bread rubbed with garlic.